Keybase is a cryptographically secure, popular tool to verify identities, and provide secure groups, files and chats.
We are using keybase filesystem (KBFS) for securely sharing encrypted files (containing keys, passwords, etc). This announcement explains the high-level, this documentation page goes into further detail, and the KBFS Crypto Spec explains how their cryptography works (see the link to Saltpack, which is used for the encryption format).
Team file sharing directories are mounted to /Volumes/Keybase/team/TEAM.NAME
. For example, the helm_project file sharing would be mounted to /Volumes/Keybase/team/helm_project
(see Known issues and workarounds below).